The invention relates to spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivatives, to pharmaceutical compositions containing the same, as well as to the use of these spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivatives in therapy.
The simplest xcex1-amino acid glycine has a number of important roles in the mammalian central nervous system (CNS). Along with xcex3-aminobutyric acid (GABA), it is a major post-synaptic inhibitory transmitter in the spinal cord and brainstem, acting through ligand gated ion channels. Interaction of glycine with these receptors can be antagonized by the alkaloid strychnine. These receptors are therefore referred to as xe2x80x98strychnine sensitivexe2x80x99 glycine receptors. Glycinergic neurotransmission is important in the processing and control of visual, auditory and motor signalling. Glycine is also an obligatory co-agonist along with glutamate at the N-methyl-D-aspartate (NMDA) receptor. Glycine therefore functions in excitatory transmission by modulating the actions of glutamate, the major excitatory neurotransmitter in the CNS. In addition the amino acid plays a role in the metabolism of peptides and proteins, including the exchange of one-carbon units.
Control of the availability of glycine for any of the above processes will potentially influence their function and provide means of treating a number of diseases and conditions. Apart from metabolism, one of the major processes controlling the concentrations of free glycine in the proximity of strychnine-sensitive and strychnine-insensitive glycine receptors is the functioning of selective high affinity glycine transporters. These proteins can actively limit the spread of glycine beyond the immediate environs of receptors, thus maintaining both spatial and temporal fidelity of receptor activation, Rapid sequestering of transmitter into neuronal or glial cells via the transporter will:also conserve glycine for future release.
Glycine transporters have been cloned to reveal two major classes, GlyT-1 and GlyT-2. GlyT-1 is expressed throughout the brain with higher mRNA levels being detected in caudal areas and cellular localisation being predominantly glial. Three isoforms of GlyT-1, 1a, 1b and 1c, arising from differential splicing and exon usage have been identified by Kim et al. (Molecular Pharm. 1994, 45, 608-617). The cloning and expression of a further human isoform GlyT-1d was recently disclosed in European Patent Application EP 951543 (Allelix Neuroscience, Inc.).
GlyT-2 distribution, as indicated by immunochemistry studies, corresponds closely to that of inhibitory xe2x80x98strychnine sensitivexe2x80x99 glycine receptors, particularly in the spinal cord.
By regulating the synaptic levels of glycine, the glycine transporters GlyT-1 and GlyT-2 are expected to selectively influence the activity at NMDA receptors and at strychnine-sensitive glycine receptors, respectively.
Compounds which alter the functional activity of glycine transporters may therefore result in changes in tissue glycine levels which can be useful in the treatment of a number of disease states. Such disease states include those associated with decreased or exaggerated function of NMDA receptors, namely psychosis, depression, dementia and other forms of impaired cognition, such as attention deficit disorders. NMDA receptors have further been implicated in conditions arising from neuronal cell death and neurodegeneration such as, for example, stroke (head trauma), Alzheimer""s disease, Parkinson""s disease and Huntington""s disease. Enhanced inhibitory glycinergic transmission resulting from inhibition of GlyT-2 or GlyT-1 activity may be useful in the treatment of muscle hyperactivity associated with spasticity, myoclonus and epilepsy. Compounds elevating spinal glycine may also possess analgesic properties.
Compounds that inhibit glycine transport via the Gly-T1 or Gly-T2 transporters are disclosed in WO 971451.15 (TROPHIX PHARM. INC.), in WO 97/45423 (TROPHIX PHARM. INC.), in WO 99/34790 (ALLELIX NEUROSCIENCE INC.) and in WO 00/07978 (AKZO NOBEL N. V.) as compounds useful in the treatment of the neurological and neuropsychiatric disorders discussed above. There exists a need for additional compounds suitable for the treatment of psychiatric and neurological disorders, especially for compounds having a selective pharmacological profile.
It has now been found that spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivatives having the general formula I 
wherein
the dotted line represents an optional bond;
Y represents 1-4 substituents independently selected from hydrogen, halogen, (C1-6)alkyl (optionally substituted with one or more halogens), (C1-6)alkyloxy (optionally substitued with one or more halogens or with (C3-6)cycloalkyl), (C2-6)alkenyloxy, (C2-6)alkynyloxy, (C3-6)cycloalkyloxy, (C6-12)aryloxy, (C7-15)arylalkyloxy, heteroaryloxy, heteroarylalkyloxy, SR3, NR3R4, OSO2R5 and NR3SO2R4;
2 substituents Y may together form Oxe2x80x94(CH2)nxe2x80x94O or Oxe2x80x94(CF2)nxe2x80x94O, where n is 1 or 2; or Y represents a fused (C5-6)aryl group;
X represents 1-3 substituents independently selected from hydrogen, halogen, hydroxy, (C1-4)alkyloxy, SR3, NR3SO2R4 and (C1-4)alkyl, optionally substituted with halogen;
R1 is hydrogen, (C1-4)alkyl or (C6-12)aryl;
R2, R3 and R4 are independently hydrogen or (C1-4)alkyl;
R5 is (C1-4)alkyl (optionally substituted with one or more halogens) or (C6-12)aryl (optionally substituted with (C1-4)alkyl); or a pharmaceutically acceptable salt thereof, selectively inhibit glycine transport by the human GlyT-1 transporter as compared to the human GlyT-2 transporter, and can be used in the treatment or prevention of schizophrenia, depression, dementia and other forms of impaired cognition, or of neurodegenerative diseases like Alzheimer""s, Parkinson""s and Huntington""s disease, or of muscle hyperactivity associated with spasticity, myoclonus and epilepsy.
The term (C1-6)alkyl, as used in the definition of formula 1, means a branched or straight chain alkyl group having 1-6 carbon atoms, like hexyl, pentyl, neopentyl (2,2-dimethylpropyl), butyl, isobutyl, tertiary butyl, propyl, isopropyl, ethyl and methyl. Likewise, the term (C1-4)alkyl refers to an alkyl group having 1-4 carbon atoms.
In the term (C1-6)alkyloxy, (C1-6)alkyl means a branched or an unbranched alkyl group as previously defined. The (C1-6)alkyloxy group may be substituted with 1-3 halogens or with (C1-6)cycloalkyl, which means a cyclic alkyl group having 3-6 carbon atoms, like cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl. Examples of such substituted (C1-6)alkyloxy groups are trifluoromethyloxy and cyclopropylmethyloxy. The term halogen means F, Cl, Br, or I. When halogen is a substituent at an alkyl group, F is preferred. A preferred halogen substituted alkyl group is trifluoromethyl. The term (C2-6)alkenyl, such as used in the term (C2-4)alkenyloxy, means a branched or straight chain alkenyl group having 2-6 carbon atoms, such as ethenyl (vinyl), 2-propenyl (allyl), isopropenyl and 2-butenyl.
The term(C2-6)alkynyl, such as used in the term (C2-6)alkynyloxy, means a branched or straight chain alkynyl group having 2-6 carbon atoms, such as propargyl.
In the term (C6-12)aryloxy, as used in the definition of formula I, (C6-12)aryl means an aromatic hydrocarbon group having 6-12 carbon atoms, such as phenyl, naphthyl, tetrahydronaphthyl, indenyl or biphenyl. These aromatic groups may be substituted with halogen, or with (C1-4)alkyl or (C1-4)alkyloxy, wherein (C1-4)alkyl has the previously given meaning and may be substituted with halogen or (C1-4)alkyloxy.
The term (C7-15)arylalkyl, as used in the definition of Formula I, means an arylalkyl group having 7 to 15 carbon atoms, wherein the alkyl group is a (C1-4)alkyl group and the aryl group is a (C6-12)aryl as previously defined. Phenyl(C1-6)alkyl groups are preferred arylalkyl groups, such as benzyl.
The term heteroaryl, such as used in the term heteroaryloxy, means a substituted or unsubstituted aromatic group having 6-12 carbon atoms, including at least one heteroatom selected from N, O and S, like for example imidazolyl, thienyl, benzthienyl, quinolinyl and indolyl. The heteroaryl group may carry substituents as listed for the aryl group.
Heteroarylalkyl groups are analogs of the (7-15)arylalkyl groups, including at least one heteroatom selected from N, O and S.
In the definition of formula I, Y can represent a fused (C5-6)aryl group, which means that Y is a 5 or 6-membered aromatic ring fused to the benzene ring to which X is attached to form a (C11-12)aromatic ring system, like a naphthalene or an indene ring.
In addition to the definition of R1 the Oxe2x80x94R1 group in Formula I may be any other group from which the free acid (R1 is hydrogen) can be generated (in vivo). Such alternative acid precursors or prodrugs, such as further ester or amide derivatives, are known in the art, and are within the scope of the present invention.
The spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivatives of formula I and their salts may contain one or more stereogenic centres and may exist therefore as stereoisomers. The present invention includes these stereoisomers within its scope, as well as enantiomers of the compounds of formula I and their salts, substantially free, i.e. associated with less than 5%, preferably less than 2%, in particular less than 1% of the other enantiomer, and mixtures of such stereoisomers in any proportions including the racemic mixtures containing substantially equal amounts of the two enantiomers.
Preferred are the spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivatives of formula I wherein the dotted line represents a bond, while those compounds wherein in addition R1 and R2 are both hydrogen are more preferred. Especially preferred spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivatives of the invention, and of salts thereof, correspond to compounds of formula I wherein the dotted line is a bond, R1 and R2 are hydrogen, and wherein Y represent a para-substituent selected from chloro, bromo, (C1-4)alkyloxy, (C1-4)alkenyloxy, (C1-4)-alkynyloxy and NR3R4, and 1 or 2 meta-substituents selected among the halogens, the preferred selection being fluoro. Specific examples of preferred substitution patterns Y are: 3-fluoro-4-methyl; 3-fluoro-4-chloro; 3-fluoro-4-dimethylamino and 3,5-difluoro-4-dimethylamino. Especially preferred are compounds according to formula I wherein Y represents 3-fluoro-4-alkyloxy, in particular 3-fluoro-4-n-propoxy and 3-fluoro-4-n-butoxy, and 3,5-difluoro-4-alkyloxy.
Spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivatives of general formula I may be prepared using a sequence of reactions in which 2xe2x80x2-hydroxyacetophenone derivatives of Formula II, wherein X has the meanings as previously defined, are utilized as starting materials which are readily available either commercially or using synthesis methods known to the person skilled in the art of synthetic organic chemistry. The 2xe2x80x2-hydroxyacetophenone derivatives II are condensed with 1-methyl-4-piperidone [R is methyl; as an alternative1-benzyl-4-piperidone (R is benzyl) may be used, the benzyl group being often more easily removed than the methyl group (see Scheme C)] in methanol solution in the presence of pyrrolidine to provide N-methyl-spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine]-4(3H)-one derivatives having Formula III as shown in Scheme A. 
The spiro-keto derivatives of Formula III are subsequently treated, as shown in Scheme B, with a Grignard reagent having formula IV, wherein Y has the meaning as previously defined, in a suitable solvent, like tetrahydrofuran, to give the 4-aryl-N-methyl- or N-benzyl-spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivatives of formula V after treatment with acid. 
Alternatively, compounds according to Formula V can be prepared by conversion of a spiro-keto derivative of Formula III, wherein R is H, methyl or benzyl, to the enoltriflate derivative IIIxe2x80x3, and subsequent Suzuki coupling reaction with a phenylboronic acid derivative IVxe2x80x3 (Scheme Bxe2x80x3). 
N-Dealkylation of the compounds according to formula V using 1-chloroethyl chloroformate in a chlorinated solvent such as 1,3-dichloropropane or dichloromethane yields the intermediate 4-aryl-spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivatives of Formula VI, which are subsequently alkylated on reaction with HalCH2R2xe2x80x94COOR1, wherein R1 may be (C1-4)alkyl or (C6-12)aryl and R2 has the meaning as previously defined and Hal means halogen, preferably bromo, to give the 4-aryl-spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivatives of Formula I, as shown in Scheme C, the ester function of which may be hydrolysed to the compounds of formula I wherein R1 is hydrogen. 
Where the required Grignard reagent according to Formula IV is not commercially available it is prepared from the relevant bromoarene using a standard procedure (The Handbook of Grignard Reagents, ed. G. S. Silverman and P. E. Rakita, 1996, Marcel Dekker, N.Y.).
The compounds of the invention can be used in the treatment of schizophrenia, depression, dementia and other forms of impaired cognition, for the treatment or prevention of neurodegeneration following stroke or head trauma, for the treatment of neurodegenerative diseases like Alzheimer""s-, Parkinson""s- and Huntington""s disease, for the treatment of muscle hyperactivity associated with spasticity, myoclonus and epilepsy, for the treatment or prevention of pain, mood disorders or learning disorders.
The compounds of this invention may possess one or more stereogenic centres and can therefore be obtained as pure stereoisomers, or as a mixture of stereoisomers. Methods for asymmetric synthesis whereby the pure stereoisomers are obtained are well known in the art, e.g. synthesis with chiral induction, enantioselective enzymatic ester hydrolysis, crystallization of salts which are obtained from optically active acids and the racemic mixture, separation of stereoisomers or enantiomers using chromatography on chiral media, or on straight phase or reversed phase chromatography media. Such methods are for example described in Chirality in Industry (edited by A. N. Collins, G. N. Sheldrake and J. Crosby, 1992; John Wiley).
Pharmaceutically acceptable salts of the compounds of formula I may be obtained by treating the free base of the compounds according to formula I with a mineral acid such as hydrochloric acid, phosphoric acid, sulphuric acid, preferably hydro-chloric acid, or with an organic acid such as for example ascorbic acid, citric acid, tartaric acid, lactic acid, maleic acid, malonic acid, fumaric acid, glycolic acid, succinic acid, propionic acid, acetic acid, methanesulphonic acid and the like. Pharmaceutically acceptable salts of compounds of formula I wherein R1 is hydrogen, may be obtained by treating the acid or zwitterionic form of those compounds with an organic base or a mineral base, like sodium, potassium or lithium hydroxide.
The invention provides in a further aspect pharmaceutical compositions comprising a spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivative having general formula I, or a pharmaceutically acceptable salt thereof, in admixture with pharmaceutically acceptable auxiliaries.
The pharmaceutical compositions for use according to the invention comprise a spiro[2H-1-benzopyran-2,4xe2x80x2-piperidine] derivative having formula I or a pharmaceutically acceptable salt thereof in admixture with pharmaceutically acceptable auxiliaries, and optionally other therapeutic agents. The term xe2x80x9cacceptablexe2x80x9d means being compatible with the other ingredients of the composition and not deleterious to the recipients thereof. The compositions can be prepared in accordance with standard techniques such as for example are described in the standard reference, Gennaro et al., Remington""s Pharmaceutical Sciences, (18th ed., Mack Publishing Company, 1990, see especially Part 8: Pharmaceutical Preparations and Their Manufacture).
Compositions include e.g. those suitable for oral, sublingual, intranasal, subcutaneous, intravenous, intramuscular, local, or rectal administration, and the like, all in unit dosage forms for administration.
For oral administration, the active ingredient may be presented as discrete units, such as tablets, capsules, powders, granulates, solutions, and suspensions. For parenteral administration, the pharmaceutical composition of the invention may be presented in unit-dose or multi-dose containers, e.g. injection liquids in predetermined amounts, for example in sealed vials and ampoules, and may also be stored in a freeze dried (lyophilized) condition requiring only the addition of sterile liquid carrier, e.g. water, prior to use.
The compounds of the invention may be administered for humans in a dosage of 0.001-50 mg per kg body weight, preferably in a dosage of 0.01-20 mg per kg body weight.
The invention further includes a pharmaceutical composition, as hereinbefore described, in combination with packaging material suitable for said composition, said packaging material including instructions for the use of the composition for the use as hereinbefore described.
The invention is illustrated by the following examples.
All mass spectrometry was carried out on either a PE SCIEX API 150EX or a PE SCIEX API. 365 machine. Melting points are uncorrected and were determined using either a Leica Galen III instrument or a Leica VMHB System Kofler.